Advances in electronics have created a variety of devices having heretofore unanticipated capabilities and requirements. In many circumstances, these devices present capabilities and requirements that are particularly useful in remote or inaccessible locations where the electrical power necessary to operate the devices is not readily available. For example, remote sensors, such as might be used to measure temperature, pressure, humidity, the presence or movement of vehicles, humans and animals, or other environmental attributes, can easily be configured to acquire and transmit such data to a more accessible location. Several options are available for providing power to such devices, such as batteries and solar cells, however, each of these approaches has drawbacks.
While battery technology has advanced tremendously in recent years, any device that draws electrical energy resulting from a chemical reaction has a useful life limited by the duration of the chemical reaction. Thus, remote applications relying exclusively on batteries are inherently limited by the battery life and reliability. Environmental factors can hinder the useful life of solar energy sources used in remote locations as well. Excessive cloud cover and shifting weather patterns can make solar cells unreliable. Dust and debris deposited on the surface of solar devices by rain or other weather related effects together with normal aging can also degrade the regular operation of these devices. Due to the drawbacks associated with these and other power technologies, there remains a need for reliable power sources that can operate over long time periods in remote locations.
Different constraints apply in non-remote settings. For example, in large buildings, tens of thousands of sensors could be usefully employed to provide smart sensing and control of energy delivery and distribution, as well as sensing and reporting of environmental conditions. At present, this vision is impractical because conventional power solutions are either technically inadequate or too expensive. Fitting every sensor with a battery power supply involves the above noted performance limitations of batteries in addition to the high cost of initial installation and periodic replacement. The alternative of hard wiring a large number of sensors to a central supply would improve reliability, but would necessarily involve complex circuitry and cost that make this approach economically unviable. These deficiencies of conventional solutions are overcome by integral, long-lived power sources that produce electric power by harvesting and converting ambient energy in the manner provided by this invention.
One potential source of energy for such devices theoretically may be found in the differing temperatures that occur naturally in these remote, non-remote and less accessible locations, since it is known that thermoelectric devices can generate electric power in response to the existence of a temperature differential across the thermoelectric device. However, the distances across typical thermo electric devices are typically small, that heretofore none have been successfully configured to take advantage of the temperature variation between, for example, the ground below and the air above it.